This invention relates to a method for ascertaining the pressure and profile depth in a pneumatic vehicle tire, whereby with an array of load sensors which supplies the force signals for a two-dimensional pattern of the distribution of the force which is exerted by the vehicle tire in contact with the sensors, [the pressure] is measured when the vehicle travels over the array, and the tire pressure is determined from the force distribution independently of the type of manufacture or the model of the wheel and of the vehicles and is optionally indicated.
A method of this type for the determination of the pressure in a pneumatic vehicle tire is described in U.S. Pat. No. 5,396,817. That prior art publication describes a linear array of force sensors over which the vehicle tire rolls. The velocity can thereby be determined from the signal rise and fall as the tire runs across the load sensor array. However, the measurement of the velocity depends on the slope of the flanks of the signal for the tire pressure and is very inaccurate on account of profile factors.
However, interfering effects of the tire profile cannot be taken into consideration in this process. In particular the signal rise is significantly changed by transverse profiling of the tire, for example transverse grooves or profile grooves that run diagonally, and it can therefore be assumed that the signal rise no longer follows a linear path.
WO 2006/003467 A1, for the determination of the profile depth of a vehicle tire, describes a device and a method in which elastic means are provided so that when the tire travels over them, they are inserted into the tire profile up to a specified depth, so that they indicate, depending on whether the means inserted into the tire profile make contact with the base of the profile, whether the tire being measured has a specified minimum profile depth. The method described in this prior art document is therefore suitable only for verification of the presence of a minimum required profile depth.
DE 43 16 984 A1 relates to a method and a device for the automatic determination of the profile depth of a vehicle tire, for which purpose a triangulation unit that can travel along a measurement line is provided and by means of a measurement beam that is emitted perpendicular to the road surface measures the profile surface of a tire, the rolling direction of which is parallel to the vertical section generated by the measurement device.
The object of the invention is therefore to make available a method for the determination of the pressure and the profile depth on a pneumatic vehicle tire of a vehicle in which the influences of the tire profile can be reduced as far as possible during the pressure measurement and the tire profile can be accurately represented.
An additional object of the invention is a triangulation-based profile measurement method which also makes possible a reliable profile depth determination if the rolling direction of the tire to be measured is not aligned exactly parallel to the vertical section generated by the triangulation unit.
An additional object of the invention is a method which is less sensitive to interference from diffused or scattered light, of the type that can occur in particular if the surface of the profile is wet.
Finally, the object of the invention is also a method which, during a single pass of the tire over a device on which the method is based, makes it possible to measure the profile depth over a significant section of the circumference of the tire and over the entire width of the cover of the tire, and thus over a surface element of the profile surface.
Ultimately the triangulation-based profile depth measurement method claimed by the invention must be capable of being combined with a method for the determination of the pressure of a vehicle tire, for which purpose the problem that must be resolved is that on one hand the pressure measurement by means of load sensors must theoretically be performed on loaded vehicle tire sections, while on the other hand, as noted above, the profile depth must be measured on unloaded segments of the vehicle tire.